Simulating the sales data

Enough concepts; let's start programming. To get a clear idea of where we're heading, we start by initializing the sales data frame we will be using, with zero observations for now. We do so by defining the available categories for each factor variable, and defining empty values with the data type we need for each variable. As you can see, it has the identifiers SALE_ID and CLIENT_ID, which will allow us to link this data with the one from clients and client_messages. To understand this, let's have a look at the following code:

status_levels <- c("PENDING", "DELIVERED", "RETURNED", "CANCELLED")
protein_source_levels <- c("BEEF", "FISH", "CHICKEN", "VEGETARIAN")
continent_levels <- c("AMERICA", "EUROPE", "ASIA")
delivery_levels <- c("IN STORE", "TO LOCATION")
paid_levels <- c("YES", "NO")

sales <- data.frame(
    SALE_ID = character(),
    CLIENT_ID = character(),
    DATE = as.Date(character()),
    QUANTITY = integer(),
    COST = numeric(),
...